1. Field of the Invention
The present invention relates to an apparatus for retaining, dispensing and retrieving oilfield coiled tubing, more particularly to an improved coiled tubing reel assembly.
2. Background of the Invention
Coiled tubing, as used in the oilfield industry, refers to a generally cylindrical metal or armored tubing having an internal diameter of one half to three and one half inches. The tubing is introduced into the oil or gas well bore through wellhead control equipment to perform various tasks during the exploration, drilling, production and workover life of a well. Coiled tubing is routinely utilized to inject gas or other fluids into the well bore to inflate or activate bridges and packers, to transport electric well logging tools downhole and to perform remedial cementing and clean out operations in the well bore. Coiled tubing has also been used to transport fishing tools to the site of a well bore blockage.
Conventional coiled tubing units typically include a reel assembly for storage and dispensing of the coiled tubing, a portable tubing injector head adapted to be mounted on existing wellhead equipment to permit introduction of the tubing into the well bore, a portable power source, a control console and a crane for handling the various elements of the unit. The reel assembly typically includes a reel base or cage for supporting the reel, a rotating reel for storing and retaining the coiled tubing thereon, a drive motor to rotate the reel, a rotary fluid manifold attached to the reel for the injection of gas or liquids into the coiled tubing, a rotary electrical power connector to permit electrical power to be transferred downhole through the coiled tubing and a powered winding or spooling mechanism to control the dispensing and rewinding of the coiled tubing. The rotary electrical power connector, rotary fluid manifold, drive motor and winding mechanism are conventionally mounted external to the reel and within the confines of the reel base. Conventional coiled tubing units and reel assemblies are exemplified by units of the types disclosed in U.S. Pat. No. 3,614,019 and the patents referenced therein.
The reel assembly, injector head, power source, control console and crane are typically mounted on a single platform for transport to a well site. The reel assembly is generally the largest single component of the coiled tubing unit. The size of the coiled tubing unit platform is limited by various regulations, including Department of Transportation regulations which limit the width and height for standard tractor-trailer truck units. The size of barges or work boats used to transport the coiled tubing unit to an offshore well site may also limit the size of the coiled tubing unit.
A typical, conventional coiled tubing reel R is generally illustrated in FIG. 1. Reel assembly R illustrated in FIG. 1 is typically mounted on a skid S by way of two opposing supporting posts P. A central axle A is mounted for rotation by way of bearing assemblies B, and generally centered on the supporting posts. Secured to the axle A, internal to the posts P, are opposing flanges F and an outer reel hub H which define the space within which coiled tubing CT is retained for transportation to and from the well site in its coiled state.
To rotate the reel for coiling and uncoiling the tubing, a reversible drive motor N is typically secured to the skid as illustrated, with a drive chain D transferring rotation from the motor to the entire reel and axle structure, by way of sprocket BP mounted to the reel flange.
With the central, live axle reel arrangement, the entire tubing reel and its supporting axle turn as the tubing is uncoiled and coiled on the reel. To permit fluid to pass into and out of the coiled tubing, a rotary fluid coupling RC is mounted outside one of the tubing flanges, which is in turn connected to a fluid manifold FL by way of piping connections PI. The axle A includes a fluid passageway FP which is in communication with the coiled tubing CT via fluid tubing FT. As illustrated in FIG. 1, this arrangement requires a complicated configuration of manifold FL and rotary coupling RC connections, all mounted outside the space defined by the opposing flanges F.
In some instances, coiled tubing units are required to provide electrical power to tools mounted on the coiled tubing CT. For this purpose, in the conventional reel R, a rotary electrical connector RE is mounted to the opposite flange F for connection with an external power cable EC and an internal power cable PC. The power cable PC is typically inserted through an electrical passageway EP in the axle A and from there to the coiled tubing CT by way of a cable fitting CF. The power cable PC is initially inserted in the coiled tubing CT when the tubing is wound on reel R.
It will be appreciated that conventional reel R requires the electrical rotary connector RE and the fluid manifold FL and rotary fluid coupling RC and piping assembly PI to be outside the flanges where they are exposed and vulnerable to damage in the field. For this reason, many suppliers of coiled tubing units include a metal cage mounted about the reel and its associated peripherals, which adds to the overall dimension of the unit which, due to overall unit size constraints noted above, further limits the useable size of the coiled tubing reel. In addition, conventional reels do not lend themselves to easily removing a reel from its base assembly for changing out an empty or damaged reel to replace it with a new reel.
It would therefore be desirable to provide a more compact coiled tubing unit to maximize the length of the tubing spool or reel. It would also be desirable to mount the manifold and rotary electrical connector within the perimeter of the coiled tubing reel itself to make them less susceptible to damage and to minimize overall unit width so that more tubing can be mounted on a single tubing reel.